Preparation of alkanesulfonates



United States Patent 3,228,980 PREPARATION F ALKANESULFONATES James K. Weil, North Wales, Alexander J. Stirton, Philadelphia, Frank D. Smith, Hnntingdon Valley, and Raymond G. Bistline, In, Philadelphia, Pa, assignors to the United States of America as represented by the Secretary of Agricnitnre No Drawing. Filed Jan. 10, 1963, Ser. No. 250,716

12 Claims. (Cl. 260-513) (Granted under Title 35, US. Code (1952), sec. 266) A non-exclusive, irrevocable, royalty-free license in the invention herein described, throughout the word for all purposes of the United States Government, with the power to grant sublicenses for such purposes, is hereby granted to the Government of the United States of America.

This invention relates to the preparation of alkanesulfonates. The alkanesulfonates and associated products of this invention are useful as chemical intermediates, surface active agents, detergents, and components of detergent compositions.

An object of the present invention is to prepare long carbon chain alkanesulfonates of the general formula c n cn cn so m, wherein n is an integer from 6 to 19, M is H, Na, K, Li, NH or a substituted ammonium radical derived from a lower molecular weight amine or alkanolamine.

Another object of the present invention is to provide a process for preparing alkanesulfonates having one less carbon atom than the parent a-sulfocarboxylic acid. A further object is to obtain a product comprising a major portion of the alkanesulfonate of one less carbon atom and a minor portion of a soap of two less carbon atoms, the latter simultaneously being formed by desulfonation in the process of the present invention.

Other objects and a fuller understanding of the invention may be had by referring to the following description and claims.

We have discovered that the preparation of alkanesulfonates by the thermal degradation of a-sulfocarboxylic acids requires the presence of sodium hydroxide in excess of that needed to completely neutralize the a-sulfocarboxylic acid.

In general according to the present invention a long carbon chain a-sulfocarboxylic acid is combined with an excess of sodium hydroxide over that required to completely neutralize the sulfocarboxylic acid, preferably an amount of the hydroxide representing a two to one ratio ratio based on weight of the salt of the acid, the alkaline mixture is stirred under a nitrogen atmosphere while being heated to fusion temperature of the mixture, usually about 300 to 320 C., until the reaction is substantially complete, and the fluid mass allowed to cool. The product contain-s the sodium salt of an alkanesulfonate of one less carbon atom than the starting a-sulfocarboxylic acid. The product may be used directly in detergent formulations or the desired components may be separated therefrom as subsequently described.

The u-sulfocarboxylic acids are readily obtained by sulfonation; suitably with sulfur trioxide or chlorosulfonic acid, as indicated by the following reaction:

wherein R is a long chain alkyl radical of 6 to 19 carbon atoms; of fatty acids such as pelargonic, obtained upon oxidative cleavage of oleic acid, the individual fatty acids of an even number of carbon atoms from lauric to behenic acid, or commercially available mixtures of long chain saturated fatty acids.

Reactions in the process of our invention are illustrated as follows, with R being the long chain alkyl radical of 6 to 19 carbon atoms.

Patented Jan. 11, 1966 "ice The initial reaction of the a-sulfocarboxyl acid with the hydroxide is the partial and complete neutralization of the acidic functions, illustrated in 2 and 3.

We have found that the thermal degradation of the products of Equations 1 to 3 proceeds as follows:

he t RCHzCH(SOaH)COzH RCHiCHzCO H-j-SOa (7) heat 2RCHgCH(SO3Na)COzH 2 ROH CH(SOaNa)COzNa-j-ROH(SO H)COzH heat R 0 H2O H(S OaNa) C O Na no reaction (9) Hence, contrary to prior art such as U.S. Patent No. 2,822,387 the thermal degradation of the half-salt (monosodium salt) of the a-sulfocarboxylic acid (Equation 8) gives as a product a mixture of the disodium salt, which is stable under these conditions, and free a-sulfocarboxylic acid which degrades according to Equation 7 to give the parent fatty acid plus sulfur trioxide. It is obvious, therefore, that thermal degradation of the monosodium salt, RCH CH(SO Na)CO I-I, in the absence of alkali does not result in decarboxylation, but rather results in desulfonation.

According to the present invention, it is only in the presence of an excess of sodium hydroxide, as represented by Equation 4, that decarboxylation occurs to give the alkanesulfonate. The alkanesulfonate is the major product, but there is by-product formation of RCH=CHCO Na (Equation 5), which, in the presence of NaOH and H 0 (Equation 6) proceeds to form a soap having two less carbon atoms than the parent fatty acid.

The alkali, used in excess of neutralization (reactions 2 and 3), and that required in the simultaneous decarboxylation (reaction 4) and desulfonation (reactions 5 and 6) is preferably sodium hydroxide, although the process is considered operative when other alkali metal hydroxides such as lithium hydroxide or potassium hydroxide are admixed with sodium hydroxide.

The process of our invention permits the formation of alkanesulfonates in an inexpensive manner. Sodium alkanesulfonates can be obtained in a pure state by the process of our invention, after separation from the byproduct soap, and are not otherwise obtainable except by more expensive reactions such as the well known Strecker reaction. The Strecker reaction depends upon the conversion of a long chain alcohol to the corresponding alkyl bromide and metathesis with sodium sulfite, usually in an autoclave under moderate pressure, as illustrated:

The long chain alcohol required in Equation 10 can be obtained by hydrogenolysis or sodium reduction of esters of long chain fatty acids, but except in the case of pelargonic acid, C H CO H, only fatty acids of an even number of carbon atoms are commercially available. Thus the process of our invention has the further advantage of producing otherwise unavailable long chain alkanesulfonates of an odd number of carbon atoms, from such commercially available fatty acids as lauric, myristic, palmitic, stearic, and behenic acids.

We have found that certain conditions for operating the process of our invention are necessary to obtain a good yield of desired product. The mixture of sodium hydroxide and the disodium salt of the a-sulfo fatty acid should be homogeneous throughout, hence, stirring is required; a nitrogen atmosphere inhibits oxidation and charring and carries off Water vapor and other volatile products; the weight ratio of sodium hydroxide to disodium salt is preferably not less than 2:1, more preferably about from 2:1 to :1, to insure a fluid stirrable mass at the critical fusion temperature range of about 300-320 C., approximating the melting point of sodium hydroxide; residence time in the molten state should be suflici-ent to insure completeness of reaction and yet avoid charring and volatile product formation, suitably from 10-30 minutes at 300320 C. for 20-60 gram charges of the disodium salt; the alkaline fusion may be carried out in iron, steel, or thick walled glass vessels, preferably in glass if a neutralization or acidification step is carried out in the same vessel. The incorporation of water in the initial stage may assist thorough mixing but is not required.

The immediate fusion product, where conversion of the disodium salt has been complete, is a mixture of sodium alkanesulfonate, sodium soap, excess sodium hydroxide, sodium carbonate, sodium sulfite and sodium acetate.

This mixture may be used directly in detergent formulations; or may be partially or completely neutralized with hydrochloric, sulfuric, phosphoric, polyphosphoric, a long chain fatty acid, or an oc-SlllfO fatty acid, before entering into detergent compositions. In conversion of the disodium salt has been incomplete the immediate fusion product will necessarily contain the unconverted disodium salt of the ot-sulfo fatty acid as an ingredient.

Examples of the fusion products of our invention formed by simultaneous decarboxylation and desulfon-ation are mixtures of sodium octanesulfonate with sodium heptanoate, sodium hendecanesulfonate with sodium caprate, sodium tridecanesulfonate with sodium laurate, sodium pentadecanesulfonate with sodium myristate, sodium hep-V tadecanesulfonate with sodium palmitate, and sodium henicosanesulfonate with sodium arachidate, formed in 2.4-2.8 yield ratios of alkanesulfonate to soap, from disodium a-sulfopelargonate, disodium a-sulfolaurate, di-

sodium a-sulfomyristate, disodium a-sul-fopalmitate, disodium u-sulfostearate, and disodium wsulfobehenate, respectively.

Examples of the alkanesulfonates of our invention are sodium octanesulfonate, sodium hendecanesulfonate, sodium tridecanesulfonate, sodium pentadecanesulfonate, sodium heptadecanesulfonate, and sodium henicosanesulfonate from the alkaline decarboxylation of disodium asulfopelargonate, disodium a-sulfolaurate, disodium asulfomyristate, disodium a-sulfopalmitate, disodium 06' sulfostearate, and disodium u-sulfobehenate, respectively.

The properties of alkali metal alkanesulfonates and the unseparated fusion products are shown in Tables I and II.

The mixtures containing alkanesulfonate and soap, characterized in Table II, were obtained by adding to the alkaline reaction mixture only the .amount of aqueous acid needed to neutralize the excess alkali metal hydroxide (cf. Example III), and filtering. Since the amount of water is minimized to prevent product loss, the filter cake of alkanesulfonate and soap also contains inorganic salt, but this presents no problem since builders for detergent compositions and soaps often contain salts such as Na SO I 3PO4, NH5P3O1O, etc.

The alkanesulfonate is readily separated from the mixture by solvent partition techniques such as those described in Examples III-VII. Slight acidification con verts the soap to free fatty acid, but the alkanesulfonate is not affected. Typically, the inorganic salts are removed from an aqueous alcohol mixture and the fatty acid separated from the alkanesulfonate. by extraction with acetone or ether.

Long chain alkanesulfonic acids were prepared in a pure state from the sodium salts by means of. an ion exchange resin (of. Example VIII). Properties of the alkanesulfonic acids are shown in Table III.

Isolation of the alkanesulfonic acids permits the ready preparation of salts with ammonia, low molecular weight amines and alkanolamines. These salts are more soluble than the corresponding sodium alkanesulfonates.

Table I shows an advantage in the process of our. invention in the formation of sodium alkanesulfonates more soluble than the parent disodium salts of oc-sulfO acids; with the further advantage of a lower critical micelle concentration which means that the sodium alkanesulfonates of our invention are more effective surface active agents at lower concentrations than are the parent disodium salts of oc-SlllfO acids.

TABLE I Sodium alkanesulfonates by decarboxylation Elemental analyses percent found/thee. Critical Micrelle Sodium Krafit concentration Alkanesulpoint, Ionate C.

C H S 7 Na Percent mmoles/l.

Kralft point and CMC for parent disodium salts of asulfo acids are as follows:

oMo Krafft pomt Percent mmoles/l.

Na a-suliopalmitate 76 0. 25 6. 6 Na; a-suliostearate 91 0. 1O 2. 5

a, '22s, 'eso TABLE n Detergency and foam sodium alkanesulfonates and fusion products Detergency, measured in a Terg-O-Tometer, 60 C., as A R, the incrrelase in reflectance after Foam height, Ross-Miles Test, 60 (3., mm.

was in Detergcncy g 25% distilled 25% ,.05% plus .25 distilled% .25 plus water 300 ppm. 2% builder water 300 ppm. 2% builder 24. "5 28.8 230 i 27. 9 29. 3 31. 3 245 C 27. 7 29. 2 29. 1 230 Fusion products:

From disodium a-sulfopalmitate 26.0 28.8 30.0 250 From disodium a-sulfopalmitate d V 24. 4 29. 0 27.4 240 From disodium a-sulfostearate u 31. 2 19. 7 28.1 240 From disodium a-sulfostearate f i 32. 6 a 28. 5 28. 9 220 From dipotassium a-suliostearate z 33. 7 Related compounds:

N a a-suliopalmitate .15. 9 29. 0 Na wsuliostearateuh 18.0 28.3 Na dodecyl suliate 25. 7 21. 3 2'2. 0 Na octadecyl sulfate 32.6 31.0 30. 4

NasPsOro-NmlzOv-NMSOs builder.

b Na trideeanesulfonate has excellent wetting properties in the Draves test with a wetting time at 0.1% in distilled water of 5.4 secs. at 0., compared to 13.3 secs. for Na dorlecanesulfonate. Na tetradecanesulfonate is not soluble enough at 25 C. for'effectlve wetting.

60% Na pentadecanesulfonate, 25% Na myristate, 15% inorganic salts.

9 Inorganic salts removed. 7

e Na heptadccane snlfonate, 17% Na palmitate, 38%

TABLE III Alkarzesulfonic acids Neutraliza- Critical micelle Alkanesultion Melting v Krafit concentration ionic equivalent, point, 0. point, acid found/thee.

Percent mmoles/l.

Kraiit point much lower than room temperature. Easily soluble to form concentrated solutions at 25 C. and below.

Table II shows that the sodium alkanesulfonates and fusion products of our invention are effective detergents ..and foaming and wetting agents in hard water. This is of our invention are useful chemical intermediates as examplified by the following type reactions:

ROHzCH SO3Na RCHgGHzSOnCl 14. RCHzCHzSOzCH-RNH: RCH CH SO1NHR' a A1013 RCHzC HzSGzCl-l- RCHgCH SO nor-nomsoavwQCmor acmonismom-Q The process of our invention is applicable to substituted a-sulfo fatty acids sufficiently stable against undesirable inorganic salts.

1 Inorganic salts removed.

g 72% K heptadecanesulfonate, 28% K palmitate.

A built solution, 03% Na pentadecanesulfonate, .01% Na myristate, .01% lime soap dispersing agent, 0.2% builder, gave a AR value (in hard water of 300 ppm.) of 26.6, and a foam height of 165 mm.

A built solution in hard water, 0.3% Na heptadecanesulfonate, 01% Napalmitate, .01 lime soap dispersing agent, .2% builder, gave 21 AR value of 30.0, foam height mm.

side reactions in the presence of exces alkali at high temperatures. An example is the following where x+y= 14:

CH3 (C H 1;? H(C H2) CHgS OgNa-l-NaCO;

The nature otour invention is further illustrated by the examples which follow. Examples I and II demonstrate that, in the absence of alkali, thermal degradation of an a-sulfo fatty acid or the monosodium salt thereof results in desulfonation with recovery of the parent fatty acid. Examples III-VII demonstrate the products and process of our invention.

EXAMPLE I. THERMAL DEGRADATION OF a-SULFO PALMITIC ACID TO PALMITIC ACID BY DESULFONA- TION IN THE ABSENCE OF ALKALI A solution of 10 grams of a-sulfo-palmitic acid in ml. of o-dichlorobenzene was heated 7 hours at a reflux temperature of -175 C. and then cooled to -5 C.

and filtered. The solid residue recrystallized from ch1o roform gave a 77% yield of palmitic acid, M.P. 60.7-

61.6" C.,-neutr-alization equivalent 258.0.

EXAMPLE II.THER'MAL DEGRADATION OF SODIUM a-SULFOSTEARTC ACID TO STEA'RIC ACID A heavy Walled glass resin flask was charged with 48 grams of sodium a-sulfos'tearic acid and 50 ml. of water. The mixture was stirred continuously with a Hershberg stirrer, a stream of nitrogen gas was passed continuously over the surface, and heat was supplied to slowly raise the temperature of the mixture to 285 C. The temperature was not raised beyond this point because sublimation onto the upper portion of the resin flask took place. The subl'imate is apparently theparent fatty acid formed in Equations 10 and 11. After cooling the mixture was extracted with boiling acetone. Crystallization of the acetone extract at 0 gave stearic acid in a yield of 65%, M.P. 68.0-68.7, neutralization equivacid, yield 20% alent 291.4, found by gas-liquid chromatography to' be' excess alkali was neutralized with sulfuric acid, the mixstearic acid of 95 purity.

EXAMPLE III.-'ALKALI FUSION or DISODIUM a-sunrosrnanarn A mixture of 60 grams of sodium m-sulfostearic acid and 120 grams of sodium hydroxide pellets in aheavy walled glass flask, stirred with a I-Iershberg stirrer, was

protected from oxidation by means of a slow stream of nitrogen and heated until the reactants entered a fluid phase at just above 300 C. Water was added to the cooled reaction mixture, excess alkali was neutralized with 50% H 50 the neutral mixture was filtered and the filtrate discarded. A portion of the solid residue was withdrawn. Analysis showed a soap-detergent composition of 45% sodium heptadecanesulfon-ate, 17% sodium palmitate, 38% inorganic salts. Detergent and foaming properties of the neutralized unseparated fusion product are shown in Table 2.

The remainder of the neutralized unseparated fusion product was slightly acidified and treated with a mixture of equal volumes of ethanol, diethyl ether, and water.

The lower aqueous layer containing inorganic salts was discarded. An equal volume of water added to the ethanoldiethyl ether system cause separation of an ether layer which was dried and evaporated. Recrystallization from acetone of the residue from the ether layer gave pal-mitic acid, M.P. 60.260.5, yield 25%.

Crystallization of the main product from the aqueous ethanol phase gave sodium heptadecanesulfonate, yield The two products were thus obtained in a total yield of 90%. 7

EXAMPLE IV.ALKALI FUSION OF DISODIUM a-SULFOPALMITATE A mixture of 48 grams of disodium a-sulfopalmitate atmosphere to above the fusion point. Water was added,

decanesultonate and myristic acid.

and 100 grams of sodium hydroxide was stirred and he-ated to the fusion temperature under a nitrogen atmosphere. The fused cake was cooled below 100 C., water was added, the mixture was neutralized and slightly acidified with sulfuric acid, diluted with ethanol and heating to boiling. Inorganic salts were removed by filtration. Crystallization of the aqueous alcohol filtrate, at 0 C. gave a mixture ofsodium alkanesulfonate and fatty acid. Extraction with, boiling acetone gave myristic Crystallization of the acetone filtrate gave sodium pentadecanesulfonate, yield 55%.

EXAMPLE V.ALKALI FUSION OF DISODIITM a-SULFOMYRISTATE Sodium hydroxide, 53 grams, was added to a paste made from 27 grams of disodium a-sulfomyristate and 30 ml. of hot water, in a heavy walled glass vessel stirred with a Hershberg stirrer. The reactants were heated and stirred under a nitrogen atmosphere at 300 C. for 15 minutes. The fused cake was cooled below 100 0,

water was added, and the mixture was made slightly acid with sulfuric acid. The crude solids were filtered off,

washed, treated with boiling 95 ethanol, and filtered,

recovering.insoluble'unoonverted starting material as ,sodium ot-sulfomyristic acid in a yield of. 30%. a The product crystallized from the alcoholic solution and washed with ether was sodium tridecanesulfonate in a yield of 39%, with the analysis shown in Table I. Inctrared analysis of a Nujol m-ull showed S0 absorption at 1260-1450 cm. and 1070 cmr and the absence of CO0" at 1580 'cm.- and CO at 1740-1750 cm.-

Addition of water to the combined alcohol filtrate and ether washings caused phase separation. Laurie acid was isolated from the ether layer and identification was confirmed by a gas-liquid chromatogram.

EXAMPLE VI.ALKALI FUSION IN STEEL Sodium hydroxide, 70 grams-was added to a paste of 38 grams of disodium ot-sulfopalmitate with ml. of hot water in a steel resin flask. The mixture was-stirred with a Hershberg stirrer and heated under a-nitrogen formula EXAMPLE VII.A-LKALI FUSION OF DISODIUM V a-SULFOPELARGONATE Sodium hydroxide, 50 grams, was added to a paste of 25 grams of sodium -sulfiopelargonic acid and 50 ml. of water in a heavy walled glass vessel. The mixture was stirred with a 'Hershberg stirrer and heated under nitrogen to the fusion temperature. The fusion mixture was cooled, water was, added, excess alkalinity was neutralized with sulfuric acid and the mixture was filtered. The clearfilt'rate was extracted with butanol, the butanol layer" was evaporated, the residue was dissolved in ethanol, decolorized, and filtered. Crystallization at 0 C. gave a 30% yield of crude sodium octanesulfonate, purified by recrystallization from ethanol, with the analysis shown in Table I. Ident-ifica-tion was confirmed by infrared absorption. i

EXAMPLE VIII.A*LKANES ULFONIC ACI DS A solution of the sodium alkanesulfonate in 50% ethanol was heated with a portion of an ion exchange resin sulfonic acid (Dowex 50W-X8 in the acid form) to facilitate solution and passed through a one foot column of the resin with a bed volume of 300 ml. The aqueous ethanol solution after ion exchange was evaporated to dryness. The residue was twice crystallized from chloroform, to give the alkanesulfonic acid in a pure state with the constants listed in Table III.

We claim:

1. A process for the preparation of an alkanesulfonate comprising combining sodium hydroxide with an a-SlllfO- carboxylic acid of the general formula wherein R is an alkyl radicalhaving 6 to 19 carbon atoms, in the ratio of at least about 1.7 to 1 based on the weight of the resulting sodium salt of said acid, to give an alkaline mixture, stirring said alkaline mixture and heating it under a nitrogen atmosphere to the fusion temperature of the mixture, to' form an alkanesulfonate of the general 'wherein R has the same significance as above.

RCH CH (SO H) CO2H wherein R is selected from the group of straight carbon chain alkyl radicals having 9, 11, 13, 15, and 19 carbon atoms, respectively, in the ratio of at least about 1.7 to 1 based on the weight of the resulting sodium salt of said acid, to give an alkaline mixture, stirring said alkaline mixture and heating it under a nitrogen atmosphere to the fusion temperature of the mixture, cooling the reaction mixture, separating from the reaction mixture an alkanesulfonate of the general formula 9 wherein R has the same significance as above, contacting said alkanesulfonate in aqueous alcoholic solution with an ion exchange resin in the acid cycle, and separating from said solution an alkanesulfonic acid of the formula wherein R has the same significance as above.

8. The process of claim 7 in which R is nonyl. 9. The process of claim 7 in which R is hendecyl. 10. The process of claim 7 in which R is tridecyl. 11. The process of claim 7 in which R is pentadecyl. 12. The process of claim 7 in which R is heptadecyl.

References Cited by the Examiner UNITED STATES PATENTS Bertsch 252-513 Blades 252121 Miskel et a1 252-421 Fincke 2605 1 3 Block 2605 13 Assistant Examiners. 

1. A PROCESS FOR THE PREPARATION OF AN ALKANESULFONATE COMPRISING COMBINING SODIUM HYDROXIDE WITH AN A-SULFOCARBOXYLIC ACID OF THE GENERAL FORMULA RCH2CH(SO3H)CO2H WHEREIN R IS AN ALKYL RADICAL HAVING 6 TO 19 CARBON ATOMS, IN THE RATIO OF AT LEAST ABOUT 1.7 TO 1 BASED ON THE WEIGHT OF THE RESULTING SODIUM SALT OF SAID ACID, TO GIVE AN ALKALINE MIXTURE, STIRRING SAID ALKALINE MIXTURE AND HEATING IT UNDER A NITROGEN ATMOSPHERE TO THE FUSION TEMPERATURE OF THE MIXTURE, TO FORM AN ALKANESULFONATE OF THE GENERAL FORMULA 